Studies on an organic electroluminescent (EL) device (hereinafter, simply referred to as ‘organic EL device’) have continued from the start point of observing an organic thin film light emission by Bernanose in the 1950s to blue electroluminescence using an anthracene single crystal in 1965, and then an organic EL device having a laminated structure including functional layers of a hole layer and a light emitting layer was proposed by Tang in 1987. Since then, the organic EL device has been developed in a form in which a specific organic material layer is introduced into the device and a specific material used therein has been developed in order to enhance the efficiency and lifespan of an organic EL device.
When voltage is applied between two electrodes of the organic EL device, holes are injected into the organic material layer at the anode, and electrons are injected into the organic material layer at the cathode. When the injected holes and electrons meet each other, an exciton is formed, and then exciton falls down to a bottom state to emit light. Materials used as the organic material layer may be classified into a light-emitting material, a hole injection material, a hole transporting material, an electron transporting material, an electron injection material, and the like according to the function.
Light-emitting materials of the organic EL device may be divided into blue, green, and red light-emitting materials according to the light-emitting color. In addition, the light-emitting materials may be classified into yellow and orange light-emitting materials which are necessary for implementing a more natural color. Furthermore, a host/dopant system may be used as a light-emitting material for the purpose of enhancing color purity and light-emitting efficiency through energy transfer. Dopant materials may be divided into a fluorescent dopant using an organic material and a phosphorescent dopant using a metal complex compound including heavy atoms such as Ir and Pt. Since the development of the phosphorescent material may theoretically can enhance light-emitting efficiency by up to 4 times compared to the fluorescent material, interests in not only phosphorescent dopants, but also phosphorescent host materials have been focused.
As materials used as a hole injection layer, a hole transporting layer, a hole blocking layer, and an electron transporting layer, NPB, BCP, Alq3 and the like represented by the following Formulae have been widely known until now, and for a light-emitting material, anthracene derivatives have been reported as a fluorescent dopant/host material In particular, for the phosphorescent material having a great advantage in terms of enhancing the efficiency among the light-emitting materials, there are metal complex compounds including Ir, such as Firpic, Ir(ppy)3 and (acac)Ir(btp)2, and these materials are used as blue, green and red dopant materials. Until now, CBP exhibits excellent characteristics as a phosphorescent host material.

However, since the light-emitting materials according to the prior art are good in terms of light-emitting characteristics, but have a low glass transition temperature and thus are very poor in thermal stability, these materials fail to reach a level which is satisfactory in terms of lifespan for an organic EL device. Accordingly, there is a need for developing a light-emitting material having excellent performance.